24. Add a Second Display

Doubling your Desktop's real estate has always been one of the best things about the Mac; ever since the first expandable Macs, it's been possible to attach a second monitor (or display) and instantly be able to use it to the fullest capacity that it would support. For instance, you could hook up a small grayscale monitor in addition to your big color one, and the two monitors would act as one large, oddly-shaped screen, and you could drag your icons and windows seamlessly from one monitor to the other (watching them change from color to black-and-white and back).